Ink jet type printers employ a print head that consists of a reservoir of ink and a semiconductor chip containing ink energizing elements such as resistance heaters or piezoelectric devices. The chip is attached to a nozzle plate having a series of nozzles that expel ink from the reservoir onto a printing surface. In a thermal ink jet printer, the ink is expelled by superheating a small portion of the ink with an electric nozzle resistor located in a chamber beneath the nozzle. The boiling ink forms an expanding bubble that propels a drop of ink through the nozzle and onto the printing surface. By carefully controlling the expulsion of the ink through the nozzles and onto the printing surface, a high quality image can be created. In a printhead using piezoelectric devices as the energizing elements, ink discharge pressure is generated by mechanical displacement or vibration of the piezoelectric devices. For color printing applications, the three primary colors of cyan, magenta and yellow are provided by ejecting ink through nozzles or holes associated with an inkwell or print head containing each of the primary colors.
Due to the small amount of ink that can be stored in an ink jet print head cartridge and the limited life span of the semiconductor chip, print head cartridges are generally designed to be disposable. However, most print head cartridges used in ink jet printers today contain much less ink than the semiconductor chip is capable of expelling through its nozzles. Thus, the chip is still usable after the initial ink supply has been expended.
Various schemes have been proposed to supply ink to the print head cartridge to extend its useful life and reduce the cost of printing. For example, some ink jet printers employ a siphon connection between the primary print head cartridge ink reservoir and a remote secondary ink reservoir. As the primary ink reservoir empties, additional ink is siphoned from the secondary ink reservoir into the primary reservoir. Another approach is to use semi-permanent print head cartridges with replaceable on carrier ink reservoirs. When the print head cartridge runs out of ink, the old ink reservoir is discarded and a new ink reservoir is attached to the print head. The idea is to make better use of the expensive semiconductor chips and nozzle plates and, thus, lower the cost of printing with an ink jet printer.
The use of semi-permanent print heads with replaceable ink reservoirs may cause problems. For example, if the primary print head ink reservoir and secondary replaceable ink reservoir are not permanently connected, they may become separated and be improperly reconnected to an incompatible component. The primary print head ink reservoirs may not be compatible with the secondary ink reservoirs for a variety of reasons. For example, the colors of the inks may be different. If a secondary ink reservoir containing a blue ink is attached to a primary ink reservoir containing a yellow ink, the blue ink may mix with the yellow ink and render the ink unusable for color printing applications.
Mechanical features have been added to the primary and secondary ink reservoirs that make it impossible to connect a secondary ink reservoir to an incompatible primary ink reservoir. However, as the number of colors, dye formulations, and special requirements increases, the mechanical systems have become inadequate to cover all the possible combinations. Thus, matching the primary ink reservoir with the secondary ink reservoir has become a substantial problem.
Therefore, there is a need for an efficient, inexpensive method and apparatus for insuring that the attributes of the ink contained in a secondary on carrier ink reservoir are compatibly matched with the attributes of the ink in a primary ink reservoir. In addition, the invention should be able to prevent the ink of an incompatible cartridge from mixing with the ink of the primary cartridge.